High power, radio frequency (RF) transistor devices are commonly used in RF communication infrastructure amplifiers. These RF transistor devices typically include one or more input leads, one or more output leads, one or more transistors, one or more bias leads, and various bondwires coupling the leads to the transistor(s). In some cases, input and output circuits also may be contained within the same package that contains the device's transistor(s). More specifically, an in-package input circuit (e.g., including an input impedance matching circuit) may be coupled between a device's input lead and a control terminal (e.g., the gate) of a transistor, and an in-package output circuit (e.g., including an output impedance matching circuit) may be coupled between a current conducting terminal (e.g., the drain) of a transistor and a device's output lead.
Instantaneous signal bandwidth (ISBW)/video bandwidth (VBW) is becoming a major requirement for RF communication infrastructure amplifiers, and thus for the high-power RF transistor devices included in such amplifiers. Along with an impedance matching circuit, an RF device's output circuit also may include a baseband decoupling circuit configured to provide an AC ground down to envelope frequencies. Generally, the ISBW of the device is limited by the low frequency resonance (LFR) caused by interaction among the device's bias feeds, other inductive elements and transistor parasitic capacitance as well any capacitance associated with an output impedance matching circuit. In recent years, RF transistor devices including a baseband decoupling circuit have been developed with limited LFRs in the range of about 450 megahertz (MHz) or less, which supports ISBWs in the range of about 150 MHz or less. Although these devices are sufficient for some applications, the requirement to support wider RF bandwidth amplifiers continues to increase.
As the design and ability to scale in-package internal baseband decoupling circuits is improved to further increase the frequency of the low frequency resonance (LFR), an undesirable side effect can be insufficient damping of resonances with very low frequencies, for example in the hundreds of kilohertz (kHz) to tens of megahertz (MHz) baseband frequency range. These very low frequency (VLF) resonances present themselves as long term memory effects that can disrupt digital predistortion (DPD) correction in the channels adjacent to the primary carrier(s). Accordingly, high-power RF transistor devices are needed that include output circuits that are capable of higher LFRs and ISBWs and that are capable of mitigating disruptive VLF resonances.